The present invention relates to a driver circuit of a stepping motor which includes two coils and which rotates a rotor which is driven by the coils by setting different phases of supplied currents for the two coils.
Various motors are known. As a motor which can accurately determine a position, a stepping motor is known, and is widely in use in various devices. For example, the stepping motor is used for focusing in a camera, antivibration, positioning in a machine tool, etc. The demand for the stepping motor is especially high in OA devices which require a large current.
The driving of the stepping motor is executed normally by changing a rotational position of a rotor with phases of currents to two stator coils. Therefore, if the rotor rotates according to the phase of the current to the coil, the rotor rotates in a predetermined manner regardless of the amount of current to the coil. In general, in order to ensure that the rotor rotates reliably, a sufficiently large amount of current is used as the amount of current to the coil.
There is a demand to minimize the power consumption in electronic devices. This demand is particularly high for battery-driven portable devices or the like. On the other hand, to allow the rotor to rotate reliably, the amount of current in the driving of the stepping motor is set to a sufficient amount. This means that a redundant current is applied to the coil and redundant power is consumed.